Alloy



Patented July 4,1939

ALLOY 1 Arthur w. Peterson, North Attleboro, assignor to Metals 86Controls Corporation, At-

tleboro, Mass), a corporation of Massachusetts No Drawing. Originalapplication August 2 3,-v 1938, Serial N0. 226,328.. Divided and thisapplication December 2, 1938, Serial No. 243,527

4 Claims. (c1. 75- 165 This invention relates to alloys, and with regardto certain more specific features, to gold alloys.

This application is a division of my copending application Serial No.226,328, filed August 23,

Among the several objects of the invention may be noted the provision ofa gold alloy which may be used to manufacture either so-called on solidgold objects or gold-plated objects, which gold alloy will wear longerthan othergold alloys of similar karats and colors, when subjected tothe wear normally encountered by articles of jewelry that are worn onthe hands and wrists,

15 etc., or clothing; the provision of a gold alloy which has anexceedingly fine, close grain, which fineness and closeness of grainmake much easier the manufacture of articles from thealloy, and preventwhat is known as orange peel (surface roughness caused by abnormallylarge crystals of metal being set in relief by mechanical working of themetal such as bending and other manufacturing operations) during themanufacture of articles of jewelry from the gold alloy; the proa visionof a gold alloy which may be used either as solid gold or as gold platewhich has much greater resistance to tarnish and corrosion encounteredin atmospheric conditions and in perspiration acids, etc.; and theprovision of a goldv alloy which, hardness for hardness, is adaptedtohigher annealing and soldering temperatures in the manufacture ofjewelry articles from it than other gold alloys now available. Otherobjects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the proportions thereof, and features of composition, whichwill be exemplified in the products hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the manufacture of plated gold articles of jewelry, one of thedifiiculties encountered is the provision of a gold plate which willstand up 45 against the abrasion caused by clothing, etc.,

when the article is being worn. The gold plate on such an article isgenerally very thin, and the of similar karat and color.

is to give it greater hardness, but the resulting color, from thestandpoint of the jewelry indus-. try, is not as good as it was before.Consequently, it has been somewhat of a problem to provide a hard goldalloy in a given karat which would present a color which, for the givenkarat of the gold, would be acceptable to the jewelry industry. Thealloy which is the subject of this invention provides a metal which fora given karat and given color has much greater wear resistance thanother hitherto known gold alloys It is known to the applicant, ofcourse, that white gold, which has nickel in it, has superior resistanceto tarnish and abrasion than yellow gold of like karat. However, thebase alloy described herein makes possible the manufacture of a yellowgold alloy whose resistance to wear and corrosion compares favorablywith white gold.

In the manufacture of articles of jewelry from 7 gold, it is customaryin many cases to use a goldplated stock. In the subsequent bending,stretching, and shaping operations, etc., of the article, the gold platehas a tendency to present a rough crystalline appearance on the surface.This phenomenon is commonly called orange peel in the jewelry and alliedindustries. It is a serious defect ancl'great pains must be taken toprevent it in the manufacture of jewelry items. The present inventiondiscloses an alloy which has a very fine, close grain which to a greatextent prevents this so-called orange peel. This fine, close grain isinherent in the structure, and while fine, close grains can be obtainedin other gold alloys, it is only at the expense of much mechanicalworking. The cobalt addition, which is a provision of this invention,prevents abnormal crystal sizein the alloy. The present alloy thusprovides a metal which affords in either case, cold-worked or annealedcondition a fine, close grain.

Among the many difilculties encountered in the provision of gold alloysfor the jewelry industry, is the difliculty of tarnish and corrosion ofthe gold by atmospheric conditions and by the acids commonly present inthe perspiration of individuals. For example, in the optical goodsindustry, it is no uncommon occurrence to receive complaints fromcustomers regarding the fact that various parts of their spectacleframes have become eaten away on the surface by the skin acids, withresulting roughness and raggedness of the metal, which in turn causesskin irritation where it comes in contact with the skin. This is causedby the fact that the perspiration acids have eaten away the gold platewhich covers a plated spectacle frame. This destruction of the goldplate is a very common occurrence in all gold-plated articles of jewelrywhich come in contact with the skin of the wearer. One of the solutionsin the past has been to substitute a gold alloy for the plate which hasa richer gold content. This is a n expensive procedure and one that itis desired to avoid. The gold alloy which is the subject of the presentinvention provides a metal which has greater tarnish and corrosionresistance to skin acids, etc. than other known alloys of similar karatand color.

In the manufacture of many articles of Jewelry, D

either the gold-plated variety or the solid karat gold variety, it isnecessary many times in the course of manufacture, to submit the articleto either high annealing temperatures or high soldering temperatures.The tendency of hitherto known gold alloys of similar color has been forthe alloys to soften unduly with this treatment, creating distortion andtoo great flexibility in the finished article. For example, in themanufacture of watch cases, which are made of very thin material(relatively speaking), at one stage of the manufacture the watch casesmust be annealed, and at another point they must have the hingessoldered on. One dimculty that has been encountered is that the watchcase itself will buckle due to stresses in the metal being relieved toounevenly. Furthermore, the finished watch casewillbesosoftthatinitsuse,itisaptto twist and distort in shape, thus causing misalignment ofparts and possibly damage to the contained delicate mechanism.Furthermore, many gold or gold-plated articles of desirable color fortheir karat, wear excessively in use. This is caused by softness in thefinished article caused by necessary annealing operations during themanufacturing processes. The present gold alloy is one that provides ametal which is adapted (for given hardness) to higher annealing andsoldering temperatures. For example, if the watch case mentioned abovewere to be annealed at, say, 800' F., it would come out with a certainsoftness. If the same watch case is made out of the gold alloy which isthe subject of this invention, and is subjected to the same annealingtemperature, the resultlngcase will be harder temper than in the formercase. This means, of course, that the metal has more springiness andconsequently more resistance to bending and buckling. It will also wearlonger, an important desideratum.

The gold alloy of the present invention consists basically of gold,copper, and cobalt.

The gold content depends upon the desired karat of the gold. The presentinvention relates principally to alloys within the karat range of 8 to20; hence the proportion of gold in the alloy, by weight, may vary fromabout 33% to about 84%.

The copper content may vary from about 11% to about 67%, by weight, ofthe alloy, depending upon the color, hardness, and other qualitiesdesired of the alloy. Less than 11% copper ordinarily produces anunsatisfactory alloy.

The cobalt content may vary from about 0.1% to about 5%, by weight, ofthe alloy, about 1% being usually preferred. The cobalt, possibly incombination with the copper present, seems to act as the regulator ofgrain size in the alloy. If no cobalt is used. the grain size of thealloy Compoeition in per cent. by weight Alloy Karat Gold Copper Cobalt0.000", m flcow, hard gggg- Vkti. 5] Rock. Vick. 5 Book. Vic. 5 Rock.Vic. 5 Rock.

a a s B A 5 mm. Erichsen cup made from the above 0.030 inch thickannealed alloy showed a very smooth and silky surface, with no orangepeel. The grain size in the cup, determined microscopically, was about0.007 millimeter.

The superiority of the alloys of the present invention is evident fromthe above.

In general, the best procedure for making up the alloys of the presentinvention is first to make a base alloy containing the copper andcobalt, and then to alloy this base alloy with sold.

The effect of increasing the cobalt content is to produce a paler gold(the decolorizing effect, or paling effect, of cobalt being roughly onlyone fourth as great as that of nickel), and at the same time to increaseits resistance to corrosion, its resistance to wear, and its temper fora given anneal or working operation. It also has a tendency to give theresulting alloy a finer, closer grain if the cobalt content isincreased. The effect on the melting point of the final gold alloy ofincrease of cobalt is to raise the melting point.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above alloys without departing fromthe scope of the invention, it is intended that all matter contained inthe above description shall be interpreted as illustrative and not in alimiting sense.

I claim:

1. A gold alloy consisting of about 33 to 84% gold, 11 to 67% copper,and 0.1 to 5% cobalt.

2. A gold alloy consisting of about 33% gold, 66% copper, and 1% cobalt.

8. A gold alloy consisting of about 41.67% gold, 57.33% copper, and 1%cobalt.

4. A gold alloy consisting of about 50% gold, 49% copper, and. 1%cobalt.

ARTHUR W. PETERSON.

